Silencer or noise damper

ABSTRACT

The invention relates to a silencer ( 1 ) for noise-laden gas pipes, especially for a suction pipe and/or an exhaust pipe of an internal combustion engine, comprising an outer pipe ( 2 ) with an inlet side ( 3 ) and an outlet side ( 4 ), a plurality of diaphragm rings ( 9, 9′, 9″, ′″, 9″″ ) each with an outer surface connected ( 5 ) to the inner surface of the outer pipe ( 2 ), at least one insert ( 6 ) with an outer surface connected ( 7 ) to the inner surface of the outer pipe ( 2 ) and/or the diaphragm rings ( 9, 9′, 9″, 9′″, 9″″ ) and with a plurality of openings ( 8 ) which are closed on one side. Said insert ( 6 ) forms sub-pipes for the gas flow in the silencer, and the openings ( 8 ), which are closed on one side, open into the sub-pipes, the depth thereof being /4 in relation to the wavelength of a frequency to be silenced. At least one perforated wall ( 10, 10′, 11, 11′ ), extends between at least two diaphragm rings ( 9, 9′, 9″, 9′″, 9″″ ) whereby an outer surface is connected ( 7 ) to at least one inner surface of the two diaphragm rings ( 9, 9′, 9′″, 9″″ , wherein at least one resonance cell is fixed between the two diaphragm rings ( 9, 9′, 9″, 9′″, 9″″ ) of the perforated wall ( 10, 10′, 11, 11′ ) and the outer pipe ( 2 ).

BACKGROUND OF THE INVENTION

The invention is directed to a noise damper or silencer for pipelinescarrying noise-laden gasses, particularly for an intake line and/orexhaust gas line of an internal combustion motor. The damper comprisesan outside pipe with an admission side and a discharge side, a pluralityof diaphragm rings having a respective outside surface in communicationwith the inside surface of the outside pipe and at least one inserthaving an outside surface in communication with either the insidesurface of the outside pipe and/or of the diaphragm rings. The inserthas a plurality of openings closed at one side, and the insert formssub-lines or passages for the gas flow in the noise damper. The openingsclosed at one side open into the sub-lines and have a depth of λ/4 withreference to the wavelength λ of a frequency to be damped.

A fundamental distinction is made between three types of damper that arebased on different physical principles, namely:

1. Absorption noise dampers

What is expected of an absorption noise damper is that higher,especially bothersome frequencies are absorbed, sucked up by absorptionmaterials or, respectively, converted into frictional heat.

EP 0 834 011 B1, for example, discloses an absorption noise damper foran internal combustion motor composed of an intake pipe carrying theintake air and of a resonator housing that surrounds the former uponformation of a closed resonance space. In addition, the absorption sounddamper is equipped with an admission muff and a discharge muff, and hasopenings in the pipe wall of the intake pipe that connect the interiorof the intake pipe to the interior of the resonator. A chamber wall ofan axial sequence of a plurality of chamber walls directed transverserelative to the longitudinal axis of the intake pipe thereby forms or,respectively, form resonator chambers of different volume in theresonator housing that are hermetically limited from one another, sothat each resonator chamber communicates with the interior of the intakepipe via openings in the pipe wall of the intake pipe without bridgingchamber walls, and comprises a mutually matched dimensioning of theresonator chamber volume, of the cross-sectional area of the opening andof the thickness of the intake pipe in the region of the respectiveopening corresponding to the wall height of the openings for eachindividual resonator chamber at the position and width if a resonatorfrequency band that is respectively structurally prescribed therefor.Each opening and the appertaining resonator chamber thereforerespectively form a Helmholtz resonator tuned to the frequency band tobe absored, i.e. to be damped.

2. Reflection sound dampers

The function of reflection sound dampers is based both on reflection ofsound waves as well as on reflection of sound waves to the acousticsource and on multiplication of sound points. The damping is thereby allthe more effective when the reflection locations are more numerous.

For example, WO 97/09 527 discloses a reflection sound damper forgas-carrying pipelines having an admission, a discharge and a chamberlying between these connections in the air intake tract of an internalcombustion motor, links or diaphragms that re duce the flowcross-section of the chamber being arranged in said chamber transverseto the flow direction.

3. Interference sound dampers

In interference sound dampers, a part of the acoustic energy isextinguished when merged after covering paths of different length.

Many combinations of the sound damper types recited above are, ofcourse, known in the Prior Art. For example, DE 197 03 414 A1, whichdefines the species, discloses a specific combination of sound dampingmechanisms. This discloses a combination of a reflection sound damper inthe form of diaphragm rings connected axially following one another anda resonance damper in the form of λ/4 resonators. The high flow lossesdue to the diaphragm rings are disadvantageous in the known noisedamper; moreover, there is still not a satisfactory tunability of thefrequencies to be damped, neither in view of the range nor the broadbandquality.

SUMMARY OF THE INVENTION

The invention is therefore based on the object of developing the noisedamper of the species to the effect that the disadvantages of the PriorArt are overcome, and a tunable damping is possible particularly in thefrequency range from 1 through 20 kHz.

The present object of the invention is achieved by at least oneapertured wall that extends between at least two diaphragm rings with anoutside surface in communication with at least the inside surface of thetwo diaphragm rings, so that at least one resonance chamber is definedbetween the two diaphragm rings, the apertured wall and the outsidepipe.

It can be provided that the insert comprises essentially plate-shapedinside walls that are provided on both sides with blind holes oropenings closed at one side. The inserts are arranged essentiallycross-shaped or star-shaped in a radial cross-section and preferablyextend over essentially the entire axial length of the outside pipe.

It is also proposed that the blind holes or openings closed at one sideare arranged offset relative to one another on both sides of an insidewall.

It is also provided that the openings closed on one side are arrangedessentially in rows from the admission side to the discharge side,whereby the depth of the openings closed on one side is the same withina row and different from row to row, preferably with increasing depthfrom the admission side to the discharge side.

It is also inventively proposed that the distance between the diaphragmrings differs, preferably increasing from the admission side to thedischarge side.

A preferred embodiment of the invention is characterized in that atleast one resonance chamber and at least one hole in the apertured wallof the resonance chamber form a Helmholtz resonator that can be tuned toa frequency band to be damped via the volume of the resonance chamber,the cross-sectional area of the hole in the apertured wall of theresonance chamber and the wall thickness of the apertured wall of theresonance chamber in the region of the hole.

It can thereby be provided that the wall thickness of the apertured wallamounts to 0.6 through 5 mm, and is preferably 1 through 3 mm.

It is also proposed that one or more apertured walls arranged followingone another from the admission side to the discharge side extends or,respectively, extend over the entire axial length of the outside pipe,and preferably concentrically within the outside pipe.

It is also preferred that a plurality of resonance chambers areprovided, whereby frequency bands to be damped by neighboring resonancechambers preferably at least partially overlap and/or the resonancechambers form reflection sound dampers and/or absorption sound dampers.

It can also be provided that the diaphragm rings are provided with blindholes or openings closed at one side that open into the sub-lines orpassages

BRIEF DESCRIPTION OF THE DRAWINGS

Thereby shown are:

FIG. 1 is a perspective view of an inventive noise damper; and

FIG. 2 is a perspective view according to FIG. 1 with partially removedoutside pipe.

DESCRIPTION OF A PREFERRED EMBODIMNT

As can be derived from FIGS. 1 and 2, an inventive noise damper orsilencer 1 comprises an outside pipe 2 with an admission side 3, adischarge side 4 and a contact surface 5, an insert 6 having a contactsurface 7 and openings closed at one side or, respectively, blind holes8, a plurality of diaphragm rings 9, 9′, 9″, 9′″, 9″″, and apertureddiaphragms 10, 10′, 11, 11′ with holes 12, 12′, 13, 13′. The diaphragmrings 9, 9′, 9″, 9′″, 9″″ are arranged between the outside pipe 2 andthe insert 6 so that the contact surface 5 proceeds between the outsidepipe 2 and the diaphragm rings 9, 9′, 9″, 9′″, 9″″ and the contactsurface 7 proceeds between the diaphragm rings 9, 9′, 9″, 9′″, 9″″ andthe insert 6, whereby the insert 6 proceeds essentially concentricallywithin the outside pipe 2.

Four sub-lines or passages, which are separated from one another, areoffered in the noise damper 1 as a result of the insert 6. The blindholes 8 respectively open toward the sub-lines, are partly arranged atopposite surfaces, preferably offset, and comprise a depth that is tunedto one-fourth of the wavelength of the frequency to be damped out fromthe overall spectrum. An excellent broadband quality of the damping canbe achieved by means of a targeted variation of the depth of the blindholes 8 over the totality of the insert 6, whereby the depth increasesfrom the admission side 3 to the discharge side 4.

The apertured walls 10, 10′, 11, 11′, the diaphragm rings 9, 9′, 9″,9′″, 9″″ and the outside pipe 2 limit four resonance chambers. Theresonance: chambers represent either additional reflection sound dampersor resonance sound and also have a depth of λ/4, whereby the depthpreferably increases from the admission side to the discharge side.

It is also proposed that the outside pipe, the diaphragm rings, theinsert and/or the apertured wall or, respectively, the apertured wallsis or, respectively, are fashioned of a metal, particularly aluminum, aheat-resistant plastic, particularly a fiber-reinforced plastic, hardrubber and/or a ceramic, such as a porous sintered material.

It can also be provided that the outside pipe, the diaphragm rings, theapertured wall and/or the insert are integrally formed, preferably as analuminum diecasting.

Finally, it is proposed that the outside pipe, the insert, the openingsclosed at one side in the insert and/or the holes in the apertured wallis or, respectively, are essentially rotationally symmetrical,preferably circular, in radial section.

The invention is thus based on the surprising perception that a multiplecombination of reflection sound dampers and resonance sound dampersenables a tuning of a frequency range from 1 through 20 kHz to be dampedwithout significant flow losses given a compact structure. Thecorresponding combination is thereby based on the utilization of one ormore apertured walls, so that the diaphragm rings functions both asreflection walls as well as for the limitation of Helmholtz resonatorsupon formation of absorption sound dampers in addition to the λ/4resonators of the insert without leading to substantial flow losses.

Further features and advantages of the invention can be derived from thefollowing description wherein an exemplary embodiment of the inventionis explained in detail by way of example on the basis of schematicdrawings. dampers depending on the design of the apertured wall 10, 10′,11, 11′. A reflection sound damper is thus present when the aperturedwall 10, 10′ is formed, for example, of a thin steel sheet, whereas aresonance sound damper is present when the apertured wall 11, 11′comprises a wall thickness is a range from 0.6 through 5 mm, so thateach hole 13, 13′ together with the resonance chamber forms a Helmholtzresonator tunable to the frequency band to be damped via absorption. Theapertured walls 10, 10′, 11, 11′ not only offer an additionalpossibility of tuning a frequency band to be damped but alsosimultaneously assure a reduction of the flow losses due to theformation of eddies at the diaphragm rings 9, 9′, 9″, 9′″, 9″″. As aresult thereof, the noise damper 1 is considerably improved overallcompared to the Prior Art.

Neither the outside pipe 2 nor the apertured walls 10, 10′, 11, 11′ needbe designed circular in a radial cross-section. The resonance behaviorof every individual sound-absorbing resonance chamber is ultimatelydefined only by the oscillating air volume in view of its resonantfrequency, so that the inventive noise damper 1 can be adapted topractically any available installation space given the smallest possiblestructure.

Both individually as well as in any arbitrary combination, the featuresof the invention disclosed in the above specification, in the claims aswell as in the drawings can be critical for the realization of thevarious embodiments of the invention.

We claim:
 1. A noise damper for pipelines carrying noise-laden gasses,said noise damper comprising an outside pipe having an inside surface,an admission side, and a discharge side; a plurality of diaphragm ringshaving respective outside surfaces in communication with the insidesurface of the outside pipe; at least one aperture wall extendingbetween at least two diaphragm rings with an outside surface incommunication with at least the inside surfaces of the two diaphragmrings to form at least one resonance chamber between the two diaphragmrings, the aperture wall and the outside pipe; and at least one inserthaving an outside surface in communication with one of the insidesurface of the outside pipe, the diaphragm rings and said at least oneaperture wall, said at least one insert having a plurality of blindholes, the insert forming sub-lines for gas flow in the noise damper,and the blind holes opening into the sub-lines and having a depth of λ/4with reference to a wavelength λ of a frequency to be damped.
 2. A noisedamper according to claim 1, wherein the at least one insert comprisesessentially plate-shaped inside walls that are arranged essentially inone of a cross-shape, a star-shape and a radial cross-section, andpreferably extend over essentially the entire axial length of theoutside pipe, said essentially plate-shaped inside walls being providedon both sides with the blind holes.
 3. A noise damper according to claim2, wherein the blind holes are arranged offset relative to one anotheron both sides of an inside wall.
 4. A noise damper according to claim 1,wherein the blind holes on one side are arranged essentially in rowsfrom the admission side to the discharge side with the depth of theblind holes being the same within a row and different from row to row.5. A noise damper according to claim 4, wherein the depth of the blindholes increases from the admission side to the discharge side.
 6. Anoise damper according to claim 1, wherein the distance betweendiaphragm rings differs.
 7. A noise damper according to claim 6, whereinthe distance between diaphragm rings increases from the admission sideto the discharge side.
 8. A noise damper according to claim 1, whereinthe at least one resonator chamber and the at least one hole in theaperture wall of the resonator chamber form a Helmholtz resonator, whichis tuned to a frequency to be damped via the volume of the resonatorchamber, the cross-sectional area of the hole in the aperture wall ofthe resonator chamber and the wall thickness of the aperture wall of theresonator chamber in the region of the hole.
 9. A noise damper accordingto claim 8, wherein the wall thickness of the aperture wall is in arange of 0.6 through 5 mm.
 10. A noise damper according to claim 9,wherein the wall thickness of the aperture wall is in a range of 1through 3 mm.
 11. A noise damper according to claim 9, wherein aplurality of resonator chambers are provided, the frequency band to bedamped by neighboring resonator chambers preferably at least partiallyoverlaps and at least one of the plurality of resonator chambers forms adamper selected from a reflection sound damper and an absorption sounddamper.
 12. A noise damper according to claim 1, which includes morethan one aperture wall arranged following one another from the admissionside toward the discharge side extending along the axial length of theoutside pipe.
 13. A noise damper according to claim 12, wherein aplurality of resonator chambers are provided, whereby frequency bands tobe damped neighboring resonator chambers are partially overlapped and atleast one resonator chamber is selected from a damper includingreflection sound dampers and absorption sound dampers.
 14. A noisedamper according to claim 1, wherein the diaphragm rings are providedwith blind holes opening into sub-lines, said blind holes having a depthof λ/4 of the wavelength λ to be damped and the depth increases from theadmission side to the discharge side of the damper.
 15. A noise damperaccording to claim 1, wherein the outside pipe, the diaphragm rings, theinsert and the aperture wall are of a material selected from a groupconsisting of a metal, a heat-resistant plastic, a hard rubber and aceramic.
 16. A noise damper according to claim 15, wherein the metal isaluminum, the heat-resistant plastic is a fiber-reinforced plastic andthe ceramic is a porous sintered material.
 17. A noise damper accordingto claim 1, wherein the outside pipe, the diaphragm rings, the aperturewall and the insert are an integrally formed member.
 18. A noise damperaccording to claim 17, wherein the integrally formed member is analuminum diecasting.
 19. A noise damper according to claim 1, whereinthe outside pipe, the insert, the blind holes and the holes in theaperture walls are essentially rotationally symmetrical in the radialsection.